The invention relates to a recognizable carrier for determining physical, chemical or biochemical interactions using optical measurement methods, with a surface defining a substrate surface and having a base layer coated with reactive elements, which are in turn bonded to receptor molecules.
The invention also relates to a method for producing the recognizable carrier for determining physical, chemical or biochemical interactions using optical measurement methods, as well as applications according to the invention
Coding of micro-arrays or, in general, of analytical carriers for recognizing patterns, so as to derive various information therefrom, has become more and more important, and the demand for these codings still increases. The type of codings has meanwhile become quite diverse, while still having individual differences.
DE 600 22 043 T2 discloses a micro-array chip with pattern recognition which has a specific spot pattern of reactive elements. Selective spots are used for pattern recognition. These spots are differentiated into those having a color-generating dye or at least a material capable of accumulating such dye, and those lacking this dye. In this way, a two-dimensional pattern is generated upon demand, wherein the pattern arrangement can be stored in databases and read out. A fluorescence marker is used as such identification dye. Because the pattern recognition proposed according to the state-of-the-art is two-dimensional, the information that can be conveyed with this pattern is limited. The use of fluorescent markers may adversely affect the sensitivity of the array and requires quite a complex measurement setup.
Conversely, WO 2005/024695 A2 attempts to overcome these disadvantages based on a method from bioinformatics, which uses the ubiquitous type of marking of micro-arrays and the recognition of such markings. The pattern recognition for the analysis of the investigated reaction must be differentiated from the recognition of data specific for the respective array. Typically, the marking for pattern recognition in an array is used as a unique one-time marker which allows a user to obtain corresponding information about the array from a database. To this end, the respective marker is incubated with the probe. Data which correspond to the binding pattern in the reaction are obtained from the reaction of the target structures in the probes to be tested with the stored information on the respective array. For example, when using fluorescent markers, a different color generation is detected and analyzed between the stored information and the reaction of the target structures to be tested. These data are then typically combined with identification codes physically applied on the arrays containing general information about the array. Such identification codes may be, for example, barcodes. These types of coatings are required and important for the analysis of the measurement data from the reaction. The conventional approach mentions as a disadvantage only that the identification codes physically applied on the arrays are typically not commonly accessible and readable. The barcode cannot be determined without the key for this barcode, a barcode reader or suitable database information, so that the entire information from the analysis cannot be evaluated. Situations where the barcode has errors and/or is read in with errors also create problems. The state-of-the-art circumvents these problems by a coding which is stored as a bit code in form of binary coding of decimal numbers (BCD code) or as binary ASCII code. In this way, one or more items of information are coded for each of array, which can be decoded again accordingly by using a computer-readable medium, and different types of information can be read out in combination. This conventional method for pattern recognition has also a two-dimensional design.
Another analytic chip with two-dimensional pattern recognition which can be used as a DNA micro-array is disclosed in WO 02/18945 A2. This analytic chip operates and recognizes data similar to a barcode. The different spot fields of the array are stored in form of binary codes at a defined location on the array. A barcode has hereby a one-to-one correspondence with molecular information of the target structures affixed on the array which are characteristic for the respective probe to be analyzed. If the analytic chip is used for gene analysis, the tested DNA fragments can be identified by a different coloration in the sample.
All aforementioned analytic chips operate according to analytic methods employing special markers, typically fluorescence markers. The respective proposed pattern recognitions are used to identify the tested species, and not to recognize the carrier for the purpose of quality and authenticity control for safety of use. Faulty starting material can then be identified either not at all or only unreliably and, more particularly, not be sorted out in time before the actual analysis.
The more recent measurement methods of reflectometric interference spectroscopy (RIfS), which has recently become more widely known through different publications dealing with different aspects, is capable of working without markers. This measurement method allows the direct testing of interactions between biomolecules, for example of antibody/antigen reactions. It is based on the determination of changes in the layer thickness on specially prepared biosensors and thus allows time- and spatially resolved testing of physical, chemical and/or biomedical interactions in or on a thin layer without markers.
The biosensor is substantially composed of a two-dimensional carrier having a specially activated and pre-treated surface configured to receive through covalent bonding a reaction partner required for measuring the biomolecules. For example, when antibody/antigen reactions are to be tested, the corresponding antibody is immobilized on the two-dimensional carrier.
The reaction partner is generally selected so as to have matching recognition structures for recognizing and binding the species to be analyzed. This means that the coating is selected so as to correspond or be similar to the respective species to be analyzed.
The probe to be analyzed is then brought into contact with the specially coated carrier having the reaction partner, the biosensor. In a following incubation phase, the species to be analyzed in the sample can bond to the corresponding molecule structures of the carrier coating. The incubation phase is terminated after a predetermined time by rinsing the carrier. The interaction between the species in the sample to be analyzed and the carrier coating can be directly measured as a change in the layer thickness. The detection method is hereby based on the interference of light having a defined wavelength through reflection at the boundary surface of the thin transparent carrier layer. The obtained interference spectra can be correlated with the changes in layer thickness.
As these brief fundamental explanations already show, an aspect to be taken into consideration when performing the reflectometric interference spectroscopy relates to the specific preparation of the carrier used for the measurement, for example the antigen/antibody interactions in physiological fluids.
WO-A-2006/131225 discloses a conventional approach which describes the preparation of the carrier in more detail. Before a substance corresponding to the species to be analyzed or (optionally) derivates thereof is deposited on the carrier, the carrier surface is first activated and subsequently modified with 3-glycidyl oxypropyl trimethoxy silane (GOPTS) by applying this substance over the surface of the carrier and covering the surface of the carrier with an additional carrier, producing a sandwich arrangement. Such sandwich arrangement is advantageous, because two carriers having the same quality can be prepared simultaneously. However, this is not necessarily required. The carriers obtained in this way are left to dry in their sandwich arrangement and can subsequently, after a predetermined elapsed time, be further processed by rinsing with a suitable fluid for receiving the species to be analyzed or a derivate thereof, i.e., for selective reaction with the species or derivate. Physiological fluids which may be tested using this carrier include, inter alia, blood serum and blood plasma.
Because the reflectometric interference spectroscopy can be used for an analysis in the field of food industry, medicine and environment, including water analysis, these are subject to significantly greater requirements regarding their safety of use compared to other analytic methods. It must be ensured that the measurement result cannot be falsified by faulty starting material. Also, the increase in product piracy requires that the analytic processes and the materials used therewith can be identified and tracked.
The future application of reflectometric interference spectroscopy in sensitive areas of medicine and food industry can expect additional pressure regarding product safety. The FDA (Food and Drug Administration) in the US as well as the EMEA (European Agency for the Evaluation of Medical Products) in Europe plan to mandate proof of authenticity for drugs and medical products through certified original manufacturer data, which will be expanded to sensitive analytical methods and their required components, like the two-dimensional carriers used here for analysis.
In order to attain this goal, a so-called Data Matrix Code has already been developed as a two-dimensional code. In its best-known application, a permanent directly label inscribed with laser light is used in the field of analytical instruments and instruments in chemistry and medicine. Several predetermined code patterns, typical in the form of a square or rectangular code image, are employed herein. These are defined and described in DIN standards, and are therefore capable of providing mandatory worldwide data and product safety. However, they cannot be used for applications of reflectometric interference spectroscopy, because they may on one hand, when applied on the substrate surface, falsify the analytical results because the code information is encoded in very compact form as a pattern of dots. On the other hand, there is the additional difficulty that the code scanner required for checking the code is incapable of reading the data out and checking the data in the analytic process itself. In addition, these codes are also not sufficiently informative, because they identify the basic material, but not the actual coating.
It is therefore the object of the present invention to optimize the specific preparation of a carrier which is used for performing optical measurement methods and which is suitable to test and to determine any type of physical, chemical or biochemical interaction, wherein the carrier is optimized with respect to quality assurance so that the method can be performed more safely and with less errors, and to satisfy future regulatory requirements and restrictions.